1. Field of the Invention
The present invention relates to an inspection method for liquid crystal panels which are used to display information in a computer or similar device.
2. Background Information
Due to manufacturing problems, several percent of the liquid crystal panels manufactured are defective. The conventional method for determining whether a display is defective is by eye-inspection. A liquid crystal panel is made up of parts. A defective panel can be identified and the defective parts roughly found by observing the luminosity of the surface of the panel when it has been energized. By observing a defective panel in detail, it can be determined where the defective parts are and how the parts are defective. Eye-inspection is, however, very difficult and time consuming even for a skilled inspector.
The inspection method used for the automatic inspection of IC's may be applied to the inspection of a liquid crystal panel. This method involves pattern matching, whereby images of the item being inspected are compared with a blueprint. In contrast with the appearance of the flat surface of an IC, however, the parts on a liquid crystal panel are thick and rather three-dimensional. This causes the imprecise input of the edges of the parts. Although the apparatus used to input the image of the liquid crystal panel can be adjusted in an attempt to eliminate this imprecision, such imprecisions may none-the-less be inputted due to optical aberrations and light conditions. This imprecision makes it impossible to always identify defective parts by comparison with a template.